Get Host Key of SSH Server

Welcome Dev! In this journal article, we are going to discuss a vital aspect of SSH server security – obtaining the host key of the server. SSH server authentication requires a host key, which ensures that the connection is established with the right server. In this article, you will learn how to get the host key of SSH server.

What is SSH Server Host Key?

Before diving into the process of getting the host key, let’s understand what SSH server host key is. A host key is a cryptographic key that represents a specific SSH server. It is used to verify the identity of the server and establish a secure connection. The host key is unique to a server and is created during the initial setup of the SSH server.

The host key is stored on the server and is used during the SSH handshake process to ensure that the server is authentic. Without a valid host key, the SSH client cannot verify the identity of the server.

Why is it Important to Get Host Key of SSH Server?

Now that we have a good understanding of the host key, let’s discuss why it is important to get the host key of the SSH server before establishing a connection. The SSH server host key ensures that the connection is established with the right server and not with a malicious one. This is essential to prevent man-in-the-middle (MITM) attacks, where an attacker intercepts the communication between the client and server and impersonates the server.

Thus, obtaining the host key is a crucial step in ensuring that the connection is secure, and data transmitted over the connection is encrypted, tamper-proof, and cannot be accessed or modified by unauthorized parties.

How to Get Host Key of SSH Server?

The process of getting the host key of SSH server involves two steps:

1. Connect to the SSH server
2. Retrieve the host key

Connect to the SSH Server

To connect to the SSH server, you need an SSH client. The most popular SSH client is OpenSSH, which is available on Linux, macOS, and Windows.

Open the terminal or command prompt and type the following command:

ssh username@server_address

Replace username with your SSH username and server_address with the IP address or domain name of the SSH server.

Retrieve the Host Key

Once you are connected to the SSH server, you can retrieve the host key by running the following command:

ssh-keyscan server_address

Replace server_address with the IP address or domain name of the SSH server.

The above command will output the host key of the SSH server, which you can verify and save for future connections.

Verifying the Host Key

After retrieving the host key, it is essential to verify its authenticity to ensure that the connection is secure. You can verify the host key using the SSH client’s built-in key verification feature.

For example, on OpenSSH client, you can run the following command:

ssh-keygen -lf <path_to_host_key_file>

Replace <path_to_host_key_file> with the path to the host key file on your local machine.

The above command will output the fingerprint of the host key, which you can compare against the fingerprint provided by the SSH server administrator to ensure that it matches.

FAQ

Q1. Can I connect to an SSH server without a host key?

A1. No. The host key is an essential component of establishing a secure connection to an SSH server. Without a valid host key, the SSH client cannot verify the identity of the server and establish an encrypted and secure connection.

Q2. Can the host key be changed?

A2. Yes. The host key can be changed if the SSH server administrator requests it. However, changing the host key can result in clients seeing a warning message about the host key change, which can impact the user experience.

Q3. What happens if the host key is compromised?

A3. If the host key is compromised, it can lead to a security breach and unauthorized access to the SSH server. In such cases, the SSH server administrator must revoke the compromised key and issue a new one to ensure secure connections.

Conclusion

Getting the host key of an SSH server is an essential step in establishing a secure connection and preventing unauthorized access to the server. By following the steps outlined in this article, you can obtain the host key and verify its authenticity to ensure that your connection is secure and your data is protected.